Craft & Making
Miter Angle Calculator
Enter the corner angle or number of sides to get the miter setting.
What miter angle do I set?
A miter (also spelled mitre) cut angles the end of a board so two pieces meet cleanly at a corner. For a known corner angle, each piece is typically set to (180° − corner) ÷ 2 — so a square 90° frame uses 45° on each leg. For a regular polygon with n equal sides, the saw setting is 180° ÷ n (a hexagon uses 30°). Always cut a test pair on scrap: blade kerf, fence alignment and stock that is not truly square will open or close the joint. Compound cuts on crown moulding need bevel as well as miter and are outside this simple geometry aid. When estimating timber volume for the frame, try the board feet calculator.
Worked example
A 90° corner → miter (180 − 90) ÷ 2 = 45° on each piece. A regular hexagon (6 sides) → 180 ÷ 6 = 30° per cut.
Limits and assumptions
Plane geometry only. Does not set bevel for compound crown miters or account for blade kerf automatically.
Frequently asked questions
Inside corner versus outside corner?
The bisect formula is the same idea; orientation on the saw changes. Dry-fit a scrap pair before cutting finish stock.
Why is my wall not a true 90°?
Measure the actual corner and enter that angle. Forcing 45° on an out-of-square corner leaves a gap.
What is kerf?
Kerf is the width of material the blade removes. It can open a joint slightly — sneak up on the final cut.
Can I use a table saw instead of a miter saw?
Yes — the angles are the same; you will need a suitable crosscut sled or miter gauge setup.